Pneumatic vibrators without bearings



M. A. FONTAINE PNEUMATIC VIBRATORS WITHOUT BEARINGS Filed April 25, 1966 April 2, 1968 2 Sheets-Sheet i1 United States Patent O PNEUMATIC VIBRATORS WITHOUT BEARINGS Michel Alphonse Fontaine, Boisemont, France, assignor to Vibratechniques S.A., Paris, Fr'ance, a corporation of France Filed Apr. 25, 1966, Ser. No. 544,741 Claims priority, application France, May 13, 1965, 16,940, Patent 1,443,363 5 Claims. (Cl. 259-1) 'ABSTRACT OF THE DISCLOSURE A. pneumatic vibrator having a hollow cylinder and an inner cylinder disposed within the hollow cylinder. One of the cylinders is stationary and the other cylinder is capable of freely rolling with hypocycloidal motion relative to the stationary cylinder. A movable plate is carried by one of the cylinders and divides the space between the cylinders into two chambers. Inlet and exhaust openings are provided so as to interconnect the two chambers with a fluid pressure source and with the atmosphere, respectively.

This invention relates to pneumatic vibrators of the type which consists of a hollow cylinder, an inner cylinder of smaller diameter which is disposed within said hollow cylinder, one of said cylinders being stationary and the other cylinder being movable, the movable cylinder being capable of rolling freely with respect to the stationary cylinder without mechanical connection with any external member or,in other words, said movable cylinder does not rotate about its own axis within bearings on the stationary cylinder, but is endowed with epicycloidal or hypocycloidal motion. A single moving plate or paddle divides the space formed between the two cylinders into two chambers, said paddle being carried by one of said cylinders and capable of withdrawing into a recess formed longitudinally in said one cylinder. Admission and exhaust openings are formed in said cylinder respectively on each side of said paddle so as to put the two chambers continuously in communication respectively with a compressed-air source and with the atmosphere.

The advantages of vibrators of this type as compared with vibrators of the type comprising an eccentric mass rotatably mounted in hearings or vibrators of the multipleblade type are well known, with the result that vibrators of the type described are preferred to the others in many applications, in particular when high vibration frequencies are required. On the other hand, these vibrators are not very suitable in cases where low vibration frequencies are necessary.

The reason for this is as follows:

In this type of vibrator, the movable cylinder is endowed simultaneously with two separate movements. On

the other hand, the center of gravity of the transverse cross-section of the movable cylinder describes a circle about the geometric center of the transverse cross-section of the stationary cylinder, at an angular velocity wS, which is the actual frequency of the vibrations produced.

On the other hand, the movable cylinder is endowed with a movement of rotation about its axis at an angular velocity to! which does not play any part in the work of the vibrator since this movement does not produce any useful work.

It is demonstrated that:

D being the diameter of the outer cylinder, 07 being the diameter of the inner cylinder and e being the difference 3,376,021 Patented Apr. 2, 1968 between these diameters to which corresponds the amplitude of the vibrations.

It can be visualized that, in the case of a given diameter D, the frequency of the vibrations mg is inversely proportional to the difference in diameters e, namely to the am plitude of the vibrations.

It is also demonstrated that, in the case of a given diameter D, the energy etficiency of the vibrator is at maximum value when e=%D.

In certain cases, for example in the vibration of concrete, the frequency of vibration wg should preferably be very high, for example of the order of 20,000 rpm. This can readily be ensured, all other things being equal, by reducing the difference in diameters e and consequently the amplitude of vibrations. Although this reduction is achieved at the expense of energy efficiency since it constitutes a departure from the optimum ratio e= /3D, it nevertheless does not result in excessive consumption.

On the other hand, in other applications such as soilcompacting operations, a low vibrational frequency is necessary. However, in vibrators of the type considered as they have been designed up to the present time, it has not been possible to reduce the frequency to any substantial degree, as this presupposes an increase in the difference in diameters e. Apart from the fact that such an increase entails a corresponding increase in the volume of the chamber and consequently in air consumption which is proportional to said volume, said difference in diameter e cannot exceed an extreme value of /2D for obvious reasons of construction.

In other applications, for example in plastering appara-tuses, it is necessary to produce vibrations having a substantial amplitude. However, the amplitude, which depends on the difference in diameter 2, cannot be increased to a considerable extent for the reasons previously stated.

The aim of this invention is to circumvent the disadvantage of vibrators of the type considered while at the same time retaining the known advantages of said vibrators over those which comprise an eccentric mass rotatably mounted in bearings or multiple-blade vibrators, and consequently to increase the field of application of vibrators of the type considered.

To this end, the vibrator in accordance with the invention is characterized in that the movable cylinder is provided with an eccentric weight, with the result that the center of gravity of its transverse cross-section is displaced from the geometrical center of the transverse crosssection of its cylindrical rolling surface.

By virtue of this arrangement, the source of vibrations provided by the circular motion of the center of gravity of the transverse cross-section of the movable cylinder about the geometrical center of the transverse cross-section of the stationary cylinder is supplemented by another source of vibrations which results from the rotational movement of the eccentric cylinder about its own axis whilst this movement, as has previously been stated, did

= not produce any useful work in vibrators of the type conwhich are due to the eccentric displacement decreases at the same time as the difference in diameters e whilst the frequency mg of the vibrations resulting from the planetary motion of the movable cylinder increases in inverse ratio.

If the difference in diameters e is therefore reduced to a considerable extent, there is accordingly obtained a very high frequency mg of vibrations resulting from the planetary motion (first source), for example of the order of 60,000 rpm, and a low frequency car of vibrations produced by the eccentric weight (second source), for example of the order of 3,000 r.=p.m.

The amplitude of vibrations of the first source will be extremely small inasmuch as it is proportional to e and the work produced by these vibrations is negligible.

On the other hand, by adopting a suitable value of eccentric displacement for the movable cylinder, it will accordingly be possible to give a suitable value to the amplitude of low-frequency vibrations of the second source, and it is these vibrations which will produce useful work.

It can therefore be understood that, by making use of a vibrator which was initially designed for the purpose of generating high-frequency low-amplitude vibrations, it is possible by virtue of an extremely simple transformation of the movable cylinder to obtain vibrations of low frequency and any desired amplitude.

By virtue of this invention, vibrators of the type considered can therefore be extended to a number of new applications for which they had not originally been intended, such as ground-compacting, plastering, pile-driving and so forth.

Two forms of embodiment of the invention are illustrated by Way of example in the accompanying drawings, in which:

FIG. '1 is an axial sectional view of the first form of embodiment;

FIG. 2 is a transverse sectional view of the same form of embodiment;

FIG. 3 is a transverse sectional view of the second form of embodiment.

The pneumatic vibrator which is illustrated in FIGS. 1 and 2 is of the type which forms the subject of French Patent No. 1,099,956 of Jan. 7, 1954, in the name of Michel Fontaine.

The vibrator referred to comprises a stationary inner cylinder 1, a hollow and movable outer cylinder 2 which is adapted to rotate around said inner cylinder. Said outer cylinder is guided between two end plates 3 and 4, which are fixed with respect to the cylinder 1, and is shielded by a casing 5 which is also fixed with respect to said cylinder 1. The complete casing assembly is secured to a base plate 6 which can be attached to the apparatus to which vibrations are to be imparted.

The stationary cylinder 1 is pierced by an axial intake duct 7 which communicates with a supply pipe 8 for the admission of compressed air. Said duct 7 communicates by way of holes 9 with a longitudinal recess or groove 10 which opens at the surface of the cylinder 1 and in which a paddle or plate 11 is adapted to slide freely, the outer edge of said paddle being in contact with the internal cylindrical surface of the hollow cylinder 2 and being capable of withdrawing completely inside said groove 10.

The paddle 11 is provided with recesses 12 opposite the holes 9 for putting the duct 7 in communication with one of the chambers 13 and 14 which are formed by, and on the opposite sides of, the paddle within the space formed between the cylinders 1 and 2. The chamber 14 is connected to the atmosphere by means of exhaust openings 15 and 16 through the end-plates 3 and 4 respectively.

The operation of this vibrator is identical with that which is described in the patent cited earlier, at least insofar as concerns the setting in rotation of the movable cylinder 2.

However, in accordance with the present invention, said movable cylinder 2 is provided with an eccentric weight by virtue of the fact that the inner and outer cylindrical surfaces thereof are not coaxial. It is self-evident that said eccentric weight could also be obtained simply by adding an eccentric mass to a normal cylinder or, alternatively, by forming weight-reducing recesses in suitable locations.

Thus vibrations are created by the rolling motion of the movable cylinder 2 around the stationary cylinder 1, and vibrations are caused by the rotation of the movable cylinder 2 about its own axis by reason of the fact that said cylinder 2 is displaced off-center of the cylinder 1. As has been explained in the introductory part of this description, it is possible by increasing the frequency of the first vibrations referred to above to reduce the frequency of the second vibrations while giving these latter the desired amplitude by adopting a suitable value of eccentric displacement, whereas the amplitude of the first vibrations necessarily decreases as their frequency increases.

The vibrator which is illustrated in FIG. 3 is of the type described in French Patent No. 1,279,241 of Mar. 10, 1960 in the name of Vibratechniques, S.A. This unit differs from the preceding only in the presence of an intermediate movable cylinder 17 between the stationary cylinder 1 and movable cylinder 2. The operation of the vibrator of FIG. 3 is identical with that which is described in the patent referred-to in regard to the setting in rotation of the moving cylinders. The fact that the movable cylinder 2 is provided with an eccentric weight makes it possible in addition to obtain the results hereinabove described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a pneumatic vibrator which consists of a hollow cylinder, an inner cylinder loosely disposed within said hollow cylinder, one of said cylinders being relatively stationary and the other cylinder being relatively movable, the movable cylinder being capable of rolling freely with respect to the stationary cylinder whereby the relative movement of said inner cylinder with respect to said hollow cylinder is hypocycloidal, one of said cylinders having a lengthwise recess communicating with a space formed between the two cylinders, and plate means slideably disposed in said recess and dividing said space into two chambers;

a source of pressure fluid and means defining intake and exhaust openings communicating with said chambers on opposite sides of said plate means so that the two chambers are substantially continuously in communication respectively with said source of pressure fiuid and with atmosphere;

the improvement comprising the provision of an eccentric mass on the movable cylinder so that the center of gravity thereof is displaced radially from the geometrical center thereof.

2. A pneumatic vibrator according to claim 1, includin g housing means having a central chamber;

wherein said inner cylinder is rigidly connected to said housing means and extends through said central chamber;

wherein said hollow cylinder encircles and is rotatably supported upon said inner cylinder;

wherein said exhaust openings are disposed in the walls of said housing means; and

wherein said hollow cylinder has a peripheral surface eccentric with the inner surface thereof.

3. A pneumatic vibrator according to claim 2, wherein said inner cylinder has a substantially coaxial opening therein communicating with said source of pressure fluid and a plurality of radially disposed openings communicating between said central opening and said recess; and

wherein said plate means has a plurality of grooves in one side thereof extending through the radially inner edge thereof and communicating with said space,

4. A pneumatic vibrator according to claim 2, including an intermediate hollow cylinder loosely encircling said inner cylinder within said space, said chambers being disposed between the outer surface of the inner cylinder and the inner surface of the intermediate cylinder; and

wherein said pressure fluid urges said plate means against said inner surface of said intermediate cylinder. 5. A vibrator for actuation by pressure fluid comprising:

an outer hollow cylinder; an inner cylinder eccentrically disposed within said outer cylinder; means definirv a recess in the wall of one of said cylinders and opening toward the adjacent wall of the other cylinder; blade means slideably disposed within said recess; a source of pressure fluid; conduit means in said one cylinder for communicating between the radially inner edge portion of said recess and said source of pressure fluid, whereby the radially outer edge of said blade means is held in contact with the wall of said other cylinder to form two chambers between said cylinders on opposite sides of the blade means;

means defining an inlet aperture communicating between one of said chambers and said inner edge portion of said recess for conducting said pressure fluid;

means defining an outlet aperture connected between the other chamber and atmosphere; and

weight means on one side of one of said cylinders so that the center of gravity thereof is displaced radially from the geometrical center thereof.

References Cited UNITED STATES PATENTS 1,829,441 10/1931 Pickett et al. 2,967,048 1/1961 Fontaine 259-1 3,030,079 4/1962 Fontaine 259-1 BILLY I. WILHITE, Primary Examiner. J. M. BELL, Assistant Examiner. 

